The Harvard Conglomerate
Pin Hill's story begins over a quarter billion years ago. The hill is composed of a rare geological formation known as the "Harvard Conglomerate," found almost exclusively in this town. These tilted beds of dark gray, slate-like phyllite and pebbly conglomerate were formed from ancient layers of black mud and gravel, creating the dramatic ledges we see today.
The Stonecutting Trade
In the early 1700s, Pin Hill became a hub of industry. The slate-like quality of the rock made it perfect for quarrying. A flourishing stonecutting trade emerged, and today, you can still find gravestones cut from Pin Hill slate in many nearby old cemeteries. The steep ledges and quarry cuts visible from the trails are silent witnesses to this bustling past.
Water Power
Below the hill runs Bowers Brook, a vital resource for early Harvard residents. For over a century, the brook powered numerous small mill enterprises. The remains of old mills and the wooden mill race add another layer to the historical tapestry of the area.